In wireless communication such as in a wireless network, a digital modulated signal is used for communication in many cases. Most of the signals used for such communication are signals with envelope variation because information is superimposed on the signal in the amplitude direction. Therefore, the wireless communication device that is used for the communication is required to amplify the signal having envelope variation. On the other hand, such wireless communication device is required to have low power consumption so as to secure communication time. The amplifier for amplifying the communication signal is also required to have low power consumption and high power added efficiency. However, there is a problem in that if the above-mentioned signal having envelope variation is amplified by a nonlinear amplifier having high power added efficiency, a distortion is generated and hence the signal is deteriorated. There are proposed some methods for amplifying the signal having envelope variation with high power added efficiency.
As one of the methods, there is an amplification method called a LINC (Linear amplification with Nonlinear Component) method. In this method, the signal with envelope variation is converted into two constant envelope signals, and each of the two constant envelope signals is amplified by using a nonlinear amplifier. Then, vector addition of the two amplified constant envelope signals is performed so that the amplified signal with envelope variation is generated. Thus, the signal with envelope variation may be amplified with high power added efficiency (see, for example, Patent Document 1).    Patent Document 1: JP 06-22302 B